Tear film interferometry has been used to observe the structure and breakup characteristics of the in-vivo tear film, but has not been widely applied due to the unavailability of appropriate instruments. It is the objective of this project to design and prove feasible the fabrication of an instrument that can be used to (1)quantitatively examine the in- vivo tear film distribution on an initial fit of a contact lens, improving the likelihood of choosing a lens that is compatible with the patient; (2) examine the lipid layer of the tear film in patients with dry-eye symptomology to determine if problems are due to lipid/meibomian gland dysfunction. An optical design concept for such an instrument has been proposed that in principle should perform well and be at moderate cost. An instrument will be constructed to confirm its feasibility to perform as required. All key personnel in this project are highly qualified optical design professionals with many decades of experience in optical instrument design and optometric/ ophthalmologic expertise. PROPOSED COMMERCIAL APPLICATION: Commercial applications for Tear Film Interferometric instruments include its use in optometrists and ophthalmologists offices as an aid in fitting contact lenses, particularly in patients that have insufficient tear volume or other tear-wetting deficiencies. By observing the actual wetting pattern and tear fluid thickness distribution on the anterior surface of trial or newly-fitted contact lenses, distinctions can be made as to which lenses perform better and are thus more likely to be accepted by the patient. A low-cost, slit- lamp-mounted model of interferometer is being developed for this specific application. A full-featured, self-standing interferometer instrument will be marketed to be used in the diagnosis of tear film disorders commonly found in dry-eye disorders, and will be of particular interest to ophthalmologists dealing with disorders of the anterior surface of the eye. Tear film interferometry is particularly adept in detecting meibomian gland dysfunction, where abnormalities in the surface oil layer of the tear film can be observed and documented.